TimeSpanMap.java

  1. /* Copyright 2002-2019 CS Systèmes d'Information
  2.  * Licensed to CS Systèmes d'Information (CS) under one or more
  3.  * contributor license agreements.  See the NOTICE file distributed with
  4.  * this work for additional information regarding copyright ownership.
  5.  * CS licenses this file to You under the Apache License, Version 2.0
  6.  * (the "License"); you may not use this file except in compliance with
  7.  * the License.  You may obtain a copy of the License at
  8.  *
  9.  *   http://www.apache.org/licenses/LICENSE-2.0
  10.  *
  11.  * Unless required by applicable law or agreed to in writing, software
  12.  * distributed under the License is distributed on an "AS IS" BASIS,
  13.  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14.  * See the License for the specific language governing permissions and
  15.  * limitations under the License.
  16.  */
  17. package org.orekit.utils;

  19. import java.util.Collections;
  20. import java.util.NavigableSet;
  21. import java.util.TreeSet;

  23. import org.orekit.time.AbsoluteDate;
  24. import org.orekit.time.ChronologicalComparator;
  25. import org.orekit.time.TimeStamped;

  27. /** Container for objects that apply to spans of time.

  29.  * @param <T> Type of the data.

  31.  * @author Luc Maisonobe
  32.  * @since 7.1
  33.  */
  34. public class TimeSpanMap<T> {

  36.     /** Container for the data. */
  37.     private final NavigableSet<Transition<T>> data;

  39.     /** Create a map containing a single object, initially valid throughout the timeline.
  40.      * <p>
  41.      * The real validity of this first entry will be truncated as other
  42.      * entries are either {@link #addValidBefore(Object, AbsoluteDate)
  43.      * added before} it or {@link #addValidAfter(Object, AbsoluteDate)
  44.      * added after} it.
  45.      * </p>
  46.      * @param entry entry (initially valid throughout the timeline)
  47.      */
  48.     public TimeSpanMap(final T entry) {
  49.         data = new TreeSet<Transition<T>>(new ChronologicalComparator());
  50.         data.add(new Transition<T>(AbsoluteDate.J2000_EPOCH, entry, entry));
  51.     }

  53.     /** Add an entry valid before a limit date.
  54.      * <p>
  55.      * As an entry is valid, it truncates the validity of the neighboring
  56.      * entries already present in the map.
  57.      * </p>
  58.      * <p>
  59.      * The transition dates should be entered only once, either
  60.      * by a call to this method or by a call to {@link #addValidAfter(Object,
  61.      * AbsoluteDate)}. Repeating a transition date will lead to unexpected
  62.      * result and is not supported.
  63.      * </p>
  64.      * @param entry entry to add
  65.      * @param latestValidityDate date before which the entry is valid
  66.      * (must be different from <em>all</em> dates already used for transitions)
  67.      */
  68.     public void addValidBefore(final T entry, final AbsoluteDate latestValidityDate) {

  70.         if (data.size() == 1) {
  71.             final Transition<T> single = data.first();
  72.             if (single.getBefore() == single.getAfter()) {
  73.                 // the single entry was a dummy one, without a real transition
  74.                 // we replace it entirely
  75.                 data.clear();
  76.                 data.add(new Transition<T>(latestValidityDate, entry, single.getAfter()));
  77.                 return;
  78.             }
  79.         }

  81.         final Transition<T> previous =
  82.                 data.floor(new Transition<T>(latestValidityDate, entry, null));
  83.         if (previous == null) {
  84.             // the new transition will be the first one
  85.             data.add(new Transition<T>(latestValidityDate, entry, data.first().getBefore()));
  86.         } else {
  87.             // the new transition will be after the previous one
  88.             data.remove(previous);
  89.             data.add(new Transition<T>(previous.date,      previous.getBefore(), entry));
  90.             data.add(new Transition<T>(latestValidityDate, entry,                previous.getAfter()));
  91.         }

  93.     }

  95.     /** Add an entry valid after a limit date.
  96.      * <p>
  97.      * As an entry is valid, it truncates the validity of the neighboring
  98.      * entries already present in the map.
  99.      * </p>
  100.      * <p>
  101.      * The transition dates should be entered only once, either
  102.      * by a call to this method or by a call to {@link #addValidBefore(Object,
  103.      * AbsoluteDate)}. Repeating a transition date will lead to unexpected
  104.      * result and is not supported.
  105.      * </p>
  106.      * @param entry entry to add
  107.      * @param earliestValidityDate date after which the entry is valid
  108.      * (must be different from <em>all</em> dates already used for transitions)
  109.      */
  110.     public void addValidAfter(final T entry, final AbsoluteDate earliestValidityDate) {

  112.         if (data.size() == 1) {
  113.             final Transition<T> single = data.first();
  114.             if (single.getBefore() == single.getAfter()) {
  115.                 // the single entry was a dummy one, without a real transition
  116.                 // we replace it entirely
  117.                 data.clear();
  118.                 data.add(new Transition<T>(earliestValidityDate, single.getBefore(), entry));
  119.                 return;
  120.             }
  121.         }

  123.         final Transition<T> next =
  124.                 data.ceiling(new Transition<T>(earliestValidityDate, entry, null));
  125.         if (next == null) {
  126.             // the new transition will be the last one
  127.             data.add(new Transition<T>(earliestValidityDate, data.last().getAfter(), entry));
  128.         } else {
  129.             // the new transition will be before the next one
  130.             data.remove(next);
  131.             data.add(new Transition<T>(earliestValidityDate, next.getBefore(), entry));
  132.             data.add(new Transition<T>(next.date,            entry,            next.getAfter()));
  133.         }

  135.     }

  137.     /** Get the entry valid at a specified date.
  138.      * @param date date at which the entry must be valid
  139.      * @return valid entry at specified date
  140.      */
  141.     public T get(final AbsoluteDate date) {
  142.         final Transition<T> previous = data.floor(new Transition<T>(date, null, null));
  143.         if (previous == null) {
  144.             // there are no transition before the specified date
  145.             // return the first valid entry
  146.             return data.first().getBefore();
  147.         } else {
  148.             return previous.getAfter();
  149.         }
  150.     }

  152.     /** Get the time span containing a specified date.
  153.      * @param date date belonging to the desired time span
  154.      * @return time span containing the specified date
  155.      * @since 9.3
  156.      */
  157.     public Span<T> getSpan(final AbsoluteDate date) {
  158.         final Transition<T> previous = data.floor(new Transition<T>(date, null, null));
  159.         if (previous == null) {
  160.             // there are no transition before the specified date
  161.             // return the first valid entry
  162.             return new Span<>(data.first().getBefore(),
  163.                               AbsoluteDate.PAST_INFINITY,
  164.                               data.first().getDate());
  165.         } else {
  166.             final Transition<T> next = data.higher(previous);
  167.             return new Span<>(previous.getAfter(),
  168.                               previous.getDate(),
  169.                               next == null ? AbsoluteDate.FUTURE_INFINITY : next.getDate());
  170.         }
  171.     }

  173.     /** Extract a range of the map.
  174.      * <p>
  175.      * The object returned will be a new independent instance that will contain
  176.      * only the transitions that lie in the specified range.
  177.      * </p>
  178.      * <p>
  179.      * Consider for example a map containing objects O₀ valid before t₁, O₁ valid
  180.      * between t₁ and t₂, O₂ valid between t₂ and t₃, O₃ valid between t₃ and t₄,
  181.      * and O₄ valid after t₄. then calling this method with a {@code start}
  182.      * date between t₁ and t₂ and a {@code end} date between t₃ and t₄
  183.      * will result in a new map containing objects O₁ valid before t₂, O₂
  184.      * valid between t₂ and t₃, and O₃ valid after t₃. The validity of O₁
  185.      * is therefore extended in the past, and the validity of O₃ is extended
  186.      * in the future.
  187.      * </p>
  188.      * @param start earliest date at which a transition is included in the range
  189.      * (may be set to {@link AbsoluteDate#PAST_INFINITY} to keep all early transitions)
  190.      * @param end latest date at which a transition is included in the r
  191.      * (may be set to {@link AbsoluteDate#FUTURE_INFINITY} to keep all late transitions)
  192.      * @return a new instance with all transitions restricted to the specified range
  193.      * @since 9.2
  194.      */
  195.     public TimeSpanMap<T> extractRange(final AbsoluteDate start, final AbsoluteDate end) {

  197.         final NavigableSet<Transition<T>> inRange = data.subSet(new Transition<T>(start, null, null), true,
  198.                                                                 new Transition<T>(end,   null, null), true);
  199.         if (inRange.isEmpty()) {
  200.             // there are no transitions at all in the range
  201.             // we need to pick up the only valid object
  202.             return new TimeSpanMap<>(get(start));
  203.         }

  205.         final TimeSpanMap<T> range = new TimeSpanMap<>(inRange.first().before);
  206.         for (final Transition<T> transition : inRange) {
  207.             range.addValidAfter(transition.after, transition.getDate());
  208.         }

  210.         return range;

  212.     }

  214.     /** Get an unmodifiable view of the sorted transitions.
  215.      * @return unmodifiable view of the sorted transitions
  216.      */
  217.     public NavigableSet<Transition<T>> getTransitions() {
  218.         return Collections.unmodifiableNavigableSet(data);
  219.     }

  221.     /** Class holding transition times.
  222.      * <p>
  223.      * This data type is dual to {@link Span}, it is
  224.      * focused one transition date, and gives access to
  225.      * surrounding valid data whereas {@link Span} is focused
  226.      * on one valid data, and gives access to surrounding
  227.      * transition dates.
  228.      * </p>
  229.      * @param <S> Type of the data.
  230.      */
  231.     public static class Transition<S> implements TimeStamped {

  233.         /** Transition date. */
  234.         private final AbsoluteDate date;

  236.         /** Entry valid before the transition. */
  237.         private final S before;

  239.         /** Entry valid after the transition. */
  240.         private final S after;

  242.         /** Simple constructor.
  243.          * @param date transition date
  244.          * @param before entry valid before the transition
  245.          * @param after entry valid after the transition
  246.          */
  247.         private Transition(final AbsoluteDate date, final S before, final S after) {
  248.             this.date   = date;
  249.             this.before = before;
  250.             this.after  = after;
  251.         }

  253.         /** Get the transition date.
  254.          * @return transition date
  255.          */
  256.         @Override
  257.         public AbsoluteDate getDate() {
  258.             return date;
  259.         }

  261.         /** Get the entry valid before transition.
  262.          * @return entry valid before transition
  263.          */
  264.         public S getBefore() {
  265.             return before;
  266.         }

  268.         /** Get the entry valid after transition.
  269.          * @return entry valid after transition
  270.          */
  271.         public S getAfter() {
  272.             return after;
  273.         }

  275.     }

  277.     /** Holder for one time span.
  278.      * <p>
  279.      * This data type is dual to {@link Transition}, it
  280.      * is focused on one valid data, and gives access to
  281.      * surrounding transition dates whereas {@link Transition}
  282.      * is focused on one transition date, and gives access to
  283.      * surrounding valid data.
  284.      * </p>
  285.      * @param <S> Type of the data.
  286.      * @since 9.3
  287.      */
  288.     public static class Span<S> {

  290.         /** Valid data. */
  291.         private final S data;

  293.         /** Start of validity for the data. */
  294.         private final AbsoluteDate start;

  296.         /** End of validity for the data. */
  297.         private final AbsoluteDate end;

  299.         /** Simple constructor.
  300.          * @param data valid data
  301.          * @param start start of validity for the data
  302.          * @param end end of validity for the data
  303.          */
  304.         private Span(final S data, final AbsoluteDate start, final AbsoluteDate end) {
  305.             this.data  = data;
  306.             this.start = start;
  307.             this.end   = end;
  308.         }

  310.         /** Get the data valid during this time span.
  311.          * @return data valid during this time span
  312.          */
  313.         public S getData() {
  314.             return data;
  315.         }

  317.         /** Get the start of this time span.
  318.          * @return start of this time span
  319.          */
  320.         public AbsoluteDate getStart() {
  321.             return start;
  322.         }

  324.         /** Get the end of this time span.
  325.          * @return end of this time span
  326.          */
  327.         public AbsoluteDate getEnd() {
  328.             return end;
  329.         }

  331.     }

  333. }
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